/*
 * Alloy Analyzer 4 -- Copyright (c) 2006-2008, Felix Chang
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

package edu.mit.csail.sdg.alloy4;

import java.util.Set;
import java.util.HashSet;

/**
 * This generates unique names based on names provided by the caller.
 *
 * <p><b>Thread Safety:</b>  Safe.
 */

public final class UniqueNameGenerator {

    /** This stores the set of names we've generated so far. */
    private final Set<String> names = new HashSet<String>();

    /** Construct a UniqueNameGenerator with a blank history. */
    public UniqueNameGenerator() { }

    /**
     * Regard the provided name as "seen".
     * <p> For convenience, it returns the argument as the return value.
     */
    public synchronized String seen(String name) { names.add(name); return name; }

    /**
     * Queries whether the provided name has been "seen" or not.
     */
    public synchronized boolean hasSeen(String name) { return names.contains(name); }

    /**
     * Clear the history of previously generated names.
     */
    public synchronized void clear() { names.clear(); }

    /**
     * Generate a unique name based on the input name.
     *
     * <p> Specifically: if the name has not been generated/seen already by this generator,
     * then it is returned as is. Otherwise, we append ' to it until the name becomes unique.
     */
    public synchronized String make(String name) {
        while(!names.add(name)) name=name+"'";
        return name;
    }
}
